Grip Gadgets
ENGN 1100 Engineering Projects - May 15, 2025
Grip Gadgets introduces a suite of devices that aims to help users with hand and arm mobility issues and address gaps in existing mobility devices. These projects are made to attach to everyday items in a user’s home or everyday environment. These devices were 3D printed, and can be provided as free 3D model downloads on assistive tech and 3D printing databases. The four devices designed for this project are:
1. An ergonomic pencil grip
2. A spherical door knob opener
3. A pill bottle opener
4. A grabber for thin objects
In a team of six, I contributed to ideation, sketching, and user testing across all assistive device concepts, with a focus on the ergonomic pencil grip. For that device, I created the wooden prototypes, engineering drawings, several 3D-printed prototypes and the final design.
1.0 Ergonomic Pencil Grip
Individuals with arthritis or neuromuscular conditions often experience hand tremors, limited grip strength, and joint pain—making it difficult to hold and use standard writing instruments. Our goal was to design an affordable, and 3D-printable ergonomic pencil grip that supports a neutral wrist posture, reduces required grip strength, and eliminates pinching or twisting motions. While writing aids are not directly regulated under the Americans with Disability Act, our design aligns with the intent of ADA Standards Section 309.4, which states that operable parts should not require tight grasping, pinching, or twisting of the wrist.
1.1 Prototyping
Each prototyping iteration was improved based on feedback from one user with arthritis, and the final prototype was further tested as shown below.
Sketching & Concept Ideation:
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~100 ergonomic grip concepts focusing on wrist alignment and shape exploration
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Most promising forms resembled a computer mouse or spherical grip
Physical Prototypes:
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Wood and cardboard mockups: evaluated side handles, grip curvature, and pressure distribution
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3D-Printed Iterations: Multiple PLA prototypes tested with users with arthritis
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Designs included:
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Prototype 1: Cone with flared base; too narrow
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Prototype 2: Double-sphere grip; required too much force to hold
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Prototype 3: Rounded ergonomic base with single finger groove; users appreciated the width and round form, provided weak pencil stabilization through screwing mechanism
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Prototype 4: Rounded ergonomic base with single finger grooves; optional circular weight cavity adds mass to reduce tremors and screw eyes to avoid pinching and twisting motions when stabilizing the pencil. Users wished for softer material, screw attachments got in the way
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1.2 Testing & Evaluation
Comfort Testing:
Six participants first completed a “Trace the Words” sheet without prototype 4, then with it. Before and after each trial, they rated discomfort (1–10) and answered questions on ease of use and preferences. Success was defined as ≥80% of users reporting reduced or no increased discomfort. Additional feedback from users with arthritis focused on wrist strain, pinching, and tight grasping.
Legibility Testing:
Participants freehanded the same list of words with and without the grip. Three evaluators scored legibility (1–5). “Trace the Words” sheets were analyzed for deviations: <3 mm = 1 point; >3 mm = 5 points. Fewer points indicated higher consistency and better legibility.
1.3 Results
Comfort Testing:
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100% reported no increase in discomfort
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Participants wished for a softer material
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83% reported reduced discomfort
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Setup considered moderately difficult due to screw mechanism
Legibility Testing:
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66% of users saw a drop in legibility initially
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71.2% increase in writing inconsistency
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Users reported growing more comfortable after multiple lines—indicating potential for improved legibility over time
1.4 Assembly & Component Drawings
1.5 Final Design
The final prototype was refined based on user testing feedback. It features a fully 3D-printable assembly: a soft TPU outer shell for comfort and an insertable PLA core that securely holds the pencil without requiring a screwing mechanism, enabling easy tool-free setup. The grip encourages a neutral wrist posture, and aligns with ADA Standard Section 309.4, not requiring tight grasping, pinching, or twisting of the wrist during usage.
2.0 Spherical Door Knob Opener
Many people with arthritis or other mobility challenges struggle to open round door knobs, which require grip strength and wrist twisting. Round door knobs are not compliant with the American with Disabilities Act (ADA) Standards for Accessible Design. Standard 404.2.7 requires door knobs to allow one-hand operation, and not require tight grasping, pinching, or twisting of the wrist. The goal was to design a portable, ergonomic 3D-printable attachment that makes round door knobs easier to operate, without needing grip strength or wrist rotation.
2.1 Prototyping
Sketching & Concept Ideation:
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96 initial concepts
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Key features: lever arm, ergonomic grip, universal fit
Materials Research:
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TPU (5–15% infill) for flexible grip
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PLA for structural components
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Inspiration from RISD Material Library
Physical Prototypes:
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Cardboard + tape mockups
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Multiple 3D-printed iterations
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Tested TPU grips for ergonomic and anti-rotation design
2.2 Final Design
The final device consists of two 3D-printed components: a base opener and a detachable handle attachment. The handle attachment comes in three sizes—Small (S), Medium (M), and Large (L)—based on 2020 ergonomic hand tool survey data. Each size accommodates different hand lengths and widths and is offered with or without a hole for attaching to carabiners or hooks.
Small: Hand Length (in): ≤ 6.7, Hand Width (in): 3.00
Medium: Hand Length (in): 6.7 – 7.0, Hand Width (in): 3.15
Large: Hand Length (in): ≥ 7.0, Hand Width (in): 3.31
2.3 Testing & Evaluation
Quantitative Testing:
The final design was tested on various round door knobs across Brown University’s campus. The following metrics were recorded during each trial:
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Door opening direction (push or pull), to assess user positioning requirements
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Door weight, measured with a spring scale to understand the force needed to open
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Knob diameter and depth, recorded with a tape measure to evaluate fit and compatibility
Qualitative Evaluation:
User experience was assessed through:
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Time trials, measuring the duration from approach to door entry (including gripping and turning the knob)
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Comfort feedback, collected from a Brown student with arthritis to understand ease of use and ergonomic impact
2.4 Results
The device was tested on 13 round door knobs across Brown University, evaluating its ability to turn knobs and open doors across varying sizes, weights, and orientations.
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Success rate: 8 out of 13 doors (61.5%)
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Average operation time: ~6 seconds
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Knob diameters: 2.069"–2.328"
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Knob depths: 1.00"–2.00"
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Door weights: <5 lbs to >10 lbs
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Opening direction: Push and pull; no impact on performance
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Best results were observed on knobs with diameters between 2.228" and 2.328". Knob depth and handedness had no effect on success.
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2 failures (#1, #7): knob diameters outside optimal range
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3 failures (#5, #6, #12): doors too heavy to open with one hand, despite knob rotation. These doors exceeded the ADA limit of 5 lbs force (Standard 404.2.9), and one (#12) also failed to meet the minimum height requirement of 34" (Standard 404.2.7).
3.0 Pill Bottle Opener
Individuals with limited grip strength often struggle with opening twist-off lids such as jars, makeup bottles, toothpaste, and especially pill bottles. Many existing gadgets assist with twisting motions but fail to support the simultaneous pushing and twisting required by child-resistant pill bottles. Motivated by firsthand experience with a grandmother affected by arthritis, our team set out to design a portable, 3D-printable, and open-source pill bottle opener that minimizes discomfort by reducing the necessary grip and maintaining an ergonomic hand position.
3.1 Prototyping
Each prototyping iteration was improved based on feedback from a Brown University student with arthritis, and the final design was refined through multiple rounds of testing.
Sketching & Concept Ideation:
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~100 initial concept sketches
Low-Fidelity Prototypes:
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Cardboard and foam core models tested grip positions
3D-Printed Iterations:
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Prototype 1: Mimicked user's typical opening method; too small, caused pinpoint pressure
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Prototype 2: Larger dual-handle design with internal grip cavity; worked on some bottles but required excessive force
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Prototype 3: Introduced conical cavity to accommodate varying bottle sizes; ineffective due to poor grip
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Prototype 4: Tested new ridge geometry in PLA and TPU; TPU performed better but ridges needed refinement
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Prototype 5: Modular insert system with stair-step ridges and wider palm rest; more ergonomic and effective but bulky
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Prototype 6: Smaller handhold with rounded edges and steeper contact point; improved ergonomics and grip reliability
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Prototype 7: Replaced ridges with flexible TPU flaps to grasp and hold caps; better traction, but required a larger cavity
3.2 Testing & Evaluation
Once a functional prototype was reached, we evaluated the design using mixed methods:
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Participants: 15 individuals, including a student with arthritis
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Procedure: Users attempted to open pill bottles with the device, first without instruction, then after guided demonstration
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Metrics:
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Comfort (1–10 scale)
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Ease of use (1–10 scale)
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Social acceptability (1–10 scale, where 10 = very uncomfortable in public)
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Open-ended user feedback
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An additional evaluation involved sending the design files to a group member’s grandmother with arthritis. She successfully printed and used the device at home, offering feedback.
3.3 Results
Survey (15 participants):
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Before Instruction:
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Comfort: Median = 7
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Ease of Use: Median = 8
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Social Acceptability: Median = 3
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After Instruction:
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Comfort: Median = 9
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Ease of Use: Median = 9
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Social Acceptability: Median = 1
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Volunteer with Arthritis:
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Comfort increased from 6 to 8.5
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Ease of use increased from 6.5 to 9
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Social acceptability remained at 0 (fully acceptable)
Additional Findings:
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Many users misoriented the device pre-instruction
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Users suggested orientation guides, smaller grip sizes, and multi-size options for handholds
The grandmother in Iowa printed and tested the device with success. She highlighted the importance of proper infill (recommended: 15%) and appreciated the hand orientation graphic. She also suggested the design could expand to other containers, such as Vaseline jars or small water bottles.
3.4 Final Design
The final design was refined based on testing feedback, featuring an ergonomic, palm-shaped handhold with a visual orientation guide, a modular TPU insert with flap grips to capture and hold the cap during twisting and visual confirmation of cap removal for feedback. The device meets ADA Section 309.4 standards: it requires only one hand to operate and avoids tight grasping, pinching, or twisting of the wrist. It is fully 3D printable, easy to assemble, and open-source for accessibility.
4.0 Thin Things Grabber
Individuals with limited grip strength or fine motor control often struggle with handling thin, flexible objects like paper. These tasks require precision and dexterity that can be painful or inaccessible.
To address this, we designed a simple, portable device enabling users to grip thin objects without fine motor effort. The solution needed to be low-force, comfortable, hygienic, and made from accessible materials like silicone and 3D-printed parts.
4.1 Prototyping
Sketching & Ideation:
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96 concepts focused on slip-on fingertip tools with soft or adhesive surfaces, aiming to reduce finger strain and fit various hand shapes.
Low-Fidelity Prototypes:
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Cardboard-and-tape mockups successfully gripped paper but caused joint strain and damaged pages due to excessive adhesion.
3D-Printed Versions:
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PLA was too rigid; TPU was flexible but too smooth. Neither outperformed the unaided finger.
Pivot to Silicone:
Inspired by sticky toys, we explored silicone for its grip, softness, and cleanability.
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Petri dish mold: Effective shape and stickiness
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Finger mold: Failed due to incorrect mixing and discomfort
4.2 Final Design
PagePal is a soft, flexible silicone disc housed in a compact, 3D-printed locking case. The silicone conforms to the user’s grip, offering a gentle, grippy surface that is foldable, pressure-sensitive, and easy to clean. The 3D-printed case keeps the disc hygienic and free from dust, while its small size makes it easy to carry in a pocket or bag. This design allows users to turn pages or grip thin objects without pinching or twisting, reducing joint strain and maintaining a discreet appearance suitable for everyday use.
4.3 Testing & Evaluation
Following the ISO 9241-210 human-centered design principles, our process prioritized comfort, usability, and dignity. We ensured the device required minimal force to operate, eliminating the need for fine motor skills. The silicone material was carefully selected for its soft, textured surface, offering both tactile ease and long-term comfort. User testing helped refine the shape through custom-fit molding, and iterative feedback guided a crucial pivot from 3D-printed models to silicone-based solutions. We also paid attention to the overall user experience, designing PagePal as a pocket-sized tool that avoids the clinical appearance of traditional assistive devices.
The required usage force was kept extremely low to reduce joint pain and fatigue. The device’s diameter—around 3.5 inches—was chosen to sit comfortably in the palm, accommodating a wide range of hand sizes. Its foldable, adaptive form allowed users to mold the tool to their grip preferences, while light surface ridges enhanced friction, making it easier to use without applying additional pressure.
4.4 Results
We tested PagePal with 18 participants, including individuals with arthritis and limited grip strength.
Grip Performance:
Users consistently rated PagePal 5 out of 5 for gripping various types of paper, including printer sheets, magazines, and cardstock.
Page-Turning Efficiency:
Participants were able to flip through pages more quickly than with bare fingers. A few noted a short learning curve to adjust to the texture and feel of the silicone disc.
Comfort & Fit:
PagePal’s soft material and flexible form prevented pressure points and conformed easily to different finger sizes and grip styles, even during extended use.
Portability & Hygiene:
The 3D-printed case kept the silicone clean, and testers appreciated its discreet, compact design that fits in bags or pockets without mess.
Ease of Cleaning:
Simple cleaning methods like rinsing or wiping maintained grip performance over time, with no degradation in stickiness or form.
Average Score:
24 out of 25
User Quotes:
“Works great once you’re used to the squishiness.”
“Easy to carry—love that it stays clean.”